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Schedule of Investments (USD $) | Mar. 31, 2015
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Unrealized Gain (Loss) on Open Commodity Contracts | $ (15,855,783)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts
Open Futures Contracts, Long | United States |
Number of Contracts | 1,349 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (15,855,783)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (22.06%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL May 2015 contracts, expiring April 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMay2015ContractsExpiringApril2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (2,120,930)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMay2015ContractsExpiringApril2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.95%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMay2015ContractsExpiringApril2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL June 2015 contracts, expiring May 2015 |
Number of Contracts | 113 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJune2015ContractsExpiringMay2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,941,100)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJune2015ContractsExpiringMay2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.70%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJune2015ContractsExpiringMay2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL July 2015 contracts, expiring June 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJuly2015ContractsExpiringJune2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,960,790)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJuly2015ContractsExpiringJune2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.73%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJuly2015ContractsExpiringJune2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL August 2015 contracts, expiring July 2015 |
Number of Contracts | 113 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClAugust2015ContractsExpiringJuly2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (2,015,910)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClAugust2015ContractsExpiringJuly2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.80%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClAugust2015ContractsExpiringJuly2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL September 2015 contracts, expiring August 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClSeptember2015ContractsExpiringAugust2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,812,480)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClSeptember2015ContractsExpiringAugust2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.52%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClSeptember2015ContractsExpiringAugust2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL October 2015 contracts, expiring September 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClOctober2015ContractsExpiringSeptember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,683,410)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClOctober2015ContractsExpiringSeptember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.34%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClOctober2015ContractsExpiringSeptember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL November 2015 contracts, expiring October 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClNovember2015ContractsExpiringOctober2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,458,810)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClNovember2015ContractsExpiringOctober2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (2.03%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClNovember2015ContractsExpiringOctober2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL December 2015 contracts, expiring November 2015 |
Number of Contracts | 113 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClDecember2015ContractsExpiringNovember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (1,161,110)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClDecember2015ContractsExpiringNovember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (1.61%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClDecember2015ContractsExpiringNovember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL January 2016 contracts, expiring December 2015 |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJanuary2016ContractsExpiringDecember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (666,623)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJanuary2016ContractsExpiringDecember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (0.93%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClJanuary2016ContractsExpiringDecember2015Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL February 2016 contracts, expiring January 2016 [Member] |
Number of Contracts | 113 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClFebruary2016ContractsExpiringJanuary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (111,900)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClFebruary2016ContractsExpiringJanuary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (0.16%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClFebruary2016ContractsExpiringJanuary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL March 2016 contracts, expiring February 2016 [Member] |
Number of Contracts | 113 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMarch2016ContractsExpiringFebruary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (565,930)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMarch2016ContractsExpiringFebruary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (0.79%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClMarch2016ContractsExpiringFebruary2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Open Futures Contracts, Long | United States | NYMEX WTI Crude Oil Futures CL April 2016 contracts, expiring March 2016 [Member] |
Number of Contracts | 112 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClApril2016ContractsExpiringMarch2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Unrealized Gain (Loss) on Open Commodity Contracts | (356,790)usl_UnrealizedGainLossOnOpenCommodityFuturesContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClApril2016ContractsExpiringMarch2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
% of Partners' Capital | (0.50%)usl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = usl_NymexWtiCrudeOilFuturesClApril2016ContractsExpiringMarch2016Member / us-gaap_InvestmentTypeAxis = usl_OpenFuturesContractsLongMember
Cash Equivalents | United States |
Market Value | 50,992,391 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US
% of Partners' Capital | 70.94%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US
Cash Equivalents | United States | US Treasury Securities |
Market Value | 26,992,391 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 37.55%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S. Treasury Bills 0.05%, 7/9/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities1Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,999,753 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities1Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities1Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.08%, 7/23/2015 |
Principal Amount | 4,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities2Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 3,999,058 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities2Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 5.57%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities2Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.06%, 7/30/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities3Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,999,633 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities3Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities3Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.06%, 8/6/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities4Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,999,612 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities4Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities4Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.07%, 8/13/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities5Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,999,516 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities5Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities5Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.07%, 8/20/2015 |
Principal Amount | 1,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities6Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 999,746 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities6Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 1.39%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities6Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.07%, 8/27/2015 |
Principal Amount | 1,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities7Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 999,733 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities7Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 1.39%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities7Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.08%, 9/3/2015 |
Principal Amount | 4,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities8Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 3,998,708 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities8Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 5.56%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities8Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.10%, 9/10/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities9Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,999,145 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities9Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities9Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.12%, 9/17/2015 |
Principal Amount | 1,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities10Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 999,460 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities10Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 1.39%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_UsTreasuryBillsSecurities10Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S.Treasury Bills 0.11%, 9/24/2015 |
Principal Amount | 2,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_DerivativeInstrumentRiskAxis = usl_GroupDuplicate11Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Market Value | 1,998,924 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DerivativeInstrumentRiskAxis = usl_GroupDuplicate11Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
% of Partners' Capital | 2.78%usl_PercentageOfPartnersCapital / us-gaap_DerivativeInstrumentRiskAxis = usl_GroupDuplicate11Member / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember
Cash Equivalents | United States | US Treasury Securities | U.S. Treasury Bill 0.10%, 6/25/2015 |
Principal Amount | 4,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = usl_UsTreasuryBillSecurities1Member
Market Value | 3,999,103 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = usl_UsTreasuryBillSecurities1Member
% of Partners' Capital | 5.57%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = usl_UsTreasuryBillSecurities1Member
Cash Equivalents | United States | Money Market Funds |
Market Value | 24,000,000 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember
% of Partners' Capital | 33.39%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember
Cash Equivalents | United States | Money Market Funds | Morgan Stanley Institutional Liquidity Funds - Government Portfolio |
Principal Amount | 16,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember
Market Value | 16,000,000 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember
% of Partners' Capital | 22.26%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember
Cash Equivalents | United States | Money Market Funds | Wells Fargo Advantage Government Money Market Fund - Class I |
Principal Amount | 8,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember
Market Value | $ 8,000,000 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember
% of Partners' Capital | 11.13%usl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = usl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember

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